Advantages
Multimetric analysis (B-IBI)
Disadvantages
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Multivariate analysis (WOWSA)
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Order list:
relatively easy to
understand how scoring
criteria are derived
results can be easily
calculated by hand
allows you to think
about how particular
groups and types of
macros respond to
increasing human
disturbance
easier to incorporate
reference streams in
future years into the
index
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a single model covers
an entire region and all
the different types of
streams in that region
slightly better at
discriminating between
levels of impact
provides information on
taxa that were expected
but absent, or not
expected but present
incorporates habitat
characteristics of the
stream
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metrics and scoring
criteria should be
reevaluated before
using in a new area or
different type of
stream (e.g., valley vs.
mountain)
does not directly
incorporate habitat
characteristics
requires judgmentbased assignment of
scoring criteria that
may skew the results
if several metrics
happen to fall just to
one side of the
criterion
model development is
difficult to understand
and more difficult to
do
must rely on someone
else to run your data
through the model
updating the model
with recent reference
information that
represents natural
variability
Insect Orders
Mayflies (Ephemeroptera)
Stoneflies (Plecoptera)
Caddisflies (Trichoptera)
Non-Insect Groups
Water mites, Hydracarina (Acarina)
Scuds, sowbugs, crayfish, and pals (Crustacea)
Snails, limpets, clams, and mussels (Mollusca)
Aquatic worms (Oligochaeta, Polychaeta)
Crayfish worms (Branchiobdellida)
True flies (Diptera)
Leeches (Hirudinea)
Aquatic beetles (Coleoptera)
Dobsonflies and alderflies (Megaloptera) Hydroids (Cnidaria)
Flatworms (Turbellaria)
Aquatic moths (Lepidoptera)
Ribbon worms (Nemertea)
Dragonflies and damselflies (Odonata)
Roundworms (Nematoda)
Aquatic true bugs (Hemiptera)
Horsehair worms (Nematomorpha)
Springtails (Collembola)
Moss animals (Ectoprocta)
Sponges (Porifera)
incidental adults
Life Expectancy - Voltinism
Macroinvertebrates live in the water for anywhere from a few weeks to 100+ years! They are
also typically unable to migrate only a short distance in their lifetime. Because of these facts,
macroinvertebrates are good at integrating the effects of human activities on a stream over time.
In the case of a temporary pulse of a pollutant, you may miss the window of time during which
the pollutant was measurable in the stream if all you're measuring is the concentration of that
pollutant. Certain components of the macroinvertebrate population, however, may be heavily
depleted for months or years after such an event. Granted, they won't tell you exactly what
pollutant was present, but a change in their population will at least tell you there is a problem
that needs to be further investigated and prevented in the future.
Generally speaking, voltinism is the number of life cycles (generations) that a species may go
through during a given year. Below are several types of voltinism that are used to describe the
longevity of freshwater macroinvertebrates and examples of each.
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multivoltine - more than one generation each year; life expectancy from egg to postreproducing adult is 1/2 of a year or less - midges, blackflies, small minnow mayflies
o bivoltine - may also be used in describing life cycles with 2 generations/year
univoltine - one generation each year; life expectancy from egg to post-reproducing adult
is 1 year - many mayflies, caddisflies, and stoneflies
semivoltine - more than one year for each generation; life expectancy from egg to postreproducing adult is more than one year - freshwater mussels, many dragonflies and
stoneflies
Metamorphosis
Macroinvertebrates become mature in a variety of ways. For example, the Crustacea and
Mollusca tend to have a planktonic stage that floats around a while before settling. Once they
settle, they just get larger and larger either through molting (crustaceans) or by adding growth to
their shell (mollusks).
Insects also have some variation in the way they grow from egg to adult, but it can be broken
down into two major groups: complete metamorphosis and incomplete metamorphosis.
Complete metamorphosis involves 4 major stages (see image below). The egg hatches. Larvae
are the primary feeding and growth stage and may go through a number of molts. Once the larva
is mature, it forms a non-feeding pupal case in which it changes dramatically. The adult then
emerges from the pupal case to reproduce. Insects that go through complete metamorphosis
include flies (Diptera), beetles (Coleoptera), caddisflies (Trichoptera), and hellgrammites
(Megaloptera).
Incomplete metamorphosis involves 3 major stages (see image below). The egg hatches.
Larvae are the primary feeding and growth stage and may go through a number of molts. As the
larva becomes more mature, the wing pads develop on top of the middle and usually hind
thoracic segments. Once the larva is mature, it usually crawls from the water; splits its
exoskeleton along the upper middle; then the adult crawls out of the old skin (called exuvia once
the adult is out). Insects that go through incomplete metamorphosis include mayflies
(Ephemeroptera - which have an extra winged stage called sub-imago before they can
reproduce), stoneflies (Plecoptera), dragon and damselflies (Odonata), and true bugs
(Hemiptera). The adult mayfly in the image below is the sub-imago stage and must molt one
more time before it will be sexually mature.
Tolerance
Macroinvertebrates must live the majority, if not all, of
their life under water. Some are very tolerant to a variety
of environmental conditions, but most have adapted to
living under a particular set of environmental conditions
and are very sensitive to changes in their environment. As
human activities in a watershed change the chemistry,
temperature, and physical characteristics of streams, the
macroinvertebrates sensitive to these changes may not be
able to survive.
Changes in water temperature and the amount of fine sediment in a stream are common
challenges for macroinvertebrates, particularly when
riparian cover or soil stability is affected by the removal
of native vegetation by development, timber harvest, or
agriculture. Organic enrichment from hatcheries,
livestock, and sewage can lower the oxygen levels in
water, severely affecting most macroinvertebrates. Some
macroinvertebrate are particularly sensitive to heavy
metals in the water from mining, industry, and urban
runoff. Other forms of pollution come from a variety of
different sources including toxic oils from dams and boats; fertilizers and herbicides from pest
control, agriculture, forestry, golf courses, and urban yards; acid rain (more of a problem in the
East); and many other types of industry from paper manufacturing to dentistry.